In known rotary shears of this type (leaflet of the Fagor company from "MM Maschinenmarkt", No. 29/1989), each blade shaft is surrounded by a sleeve, on which the roller blades are axially positionable. The sleeve can be expanded due to hydraulic medium introduced between the blade shaft and the sleeve and this causes the roller blades to be clamped on the blade shaft. This has the disadvantage that all the roller blades are always either clamped on the blade shaft or displaceable thereon when unclamped. It must therefore be feared, in particular, that when a roller blade is positioned, it will alter its position again, for example due to vibrations of the machine, so that, finally, exact distances between the roller blades cannot be set. Moreover, the manipulator of the known rotary shears is designed such that the roller blades of the lower blade shaft can be adjusted only by taking along the roller blades on the upper blade shaft and the manipulator, when the roller blades on the upper blade shaft are to be adjusted individually, must perform a lifting movement in order to get free of the roller blades of the lower blade shaft. This means that the positioning of the roller blades on their blade shafts is time-consuming and complicated.